Low-temperature liquefied-gas storage reservoir

ABSTRACT

The reservoir intended for the storage of very great quantities of liquefied gas at very low temperature is provided with a heat insulating layer of very great thickness. For this purpose the insulating layer consists of juxtaposed caissons made of radial panels secured to the walls of the reservoir and of front panels resting side by side, with a clearance between one another, upon the inner radial edges of said radial panels. Struts angularly disposed between the walls of the reservoir and the front panels reinforce the construction.

United States Patent 1 Richard et a].

[ Aug. 28, 1973 LOW-TEMPERATURE LlQUEFIED-GAS STORAGE RESERVOIR [75] Inventors: Lucien Louis Richard, Neuilly sur SeiiiefKuguste i iiispr' Gilles, Paris, both of France Gall De France; Gaz Transport, Paris, France 22 Filed: Oct. 18, 1971 21 Appl.No.: 190,111

[73] Assignes:

[30] Foreign Application Priority Data Oct. 19, 1970 France 7037691 [52] US. Cl 220/9 LG, 220/15 [5 1] Int. Cl 365d 25/18 [58] Field of Search 62/45; 220/9 LG, 220/i5 [56] References Cited UNlTED STATES PATENTS 3,339,784 9/1967 Filstead, .lr. 220/15 3,093,260 6/1963 Macormack et al 220/l5 X Primary Examiner-Meyer Perlin flaivaerfiqmi'gq, 9asld C- ,qapossela A ttorney- Francis T. Carr and Theodore Ordman ABSTRACT The reservoir intended for the storage of very great quantities of liquefied gas at very low temperature is provided with a heat insulating layer of very great -thickness. For this purpose the insulating layer consists of juxtaposed caissons made of radial panels secured to the walls of the reservoir and of front panels resting side by side, with a clearance between one another, upon the inner radial edges of said radial panels. Struts angularly disposed between the walls of the reservoir and the front panels reinforce the construction.

11 Claims, 23 Drawing Figures v Patented Aug. 28, 1973 10 Sheets-Sheet 1 Patented Aug. 28, 1973 10 Sheets-Sheet 5 n J n I smwH Patented Aug. 28, 1973 10 Sheets-Sheet 4.

Patented Aug. 28, 1973 10 Sheets-Sheet 5 4w 7 J a ...v

10 Sheets-Sheet 6 Patented Aug. 28, 1973 10 Shoots-Shoot :3

Pa tented Aug. 28, 1973 3,754,675

10 Sheets-Sheet 9 Patented Aug. 28, 1973 1O Sheets-Sheet 1 0 LOW-TEMPERATURE LIQUEFIED-GAS STORAGE RESERVOIR The present invention has essentially for its object a storage reservoir for liquefied gas at very low temperature, such as for instance liquefied natural gas, the said reservoir being of the type comprising an outer resistant shell formed by a bottom wall, a sidewall and a cupola-shaped top-wall made from prestressed reinforced concrete or any other suitable, mechanically strong material such as for instance steel or light alloy, a thick layer of heat-insulating material comprising caissons made from wood, plywood or the like, filled with an insulating material such as expanded foam, perlite, rock wool or the like, the said caissons being fastened or placed side by side and covering internally the greater part of the bottom and side walls, and at least one sealing barrier bearing upon and fastened on the said heat-insulating layer, the said sealing barrier being constituted by a thin sheet of a metal which is resilient at low temperature and whose coefficient of thermal expansion is low, formed for instance by strips or bands of lnvar or'the like whose borders raised towards the interior of the reservoir are welded edge to edge on metal strips fastened on the said heat-insulating layer.

Reservoirs of this type are known and in particular reference can be made in thisconnection to French Pat. No. 1,546,524 filed in the names of the same applicants, concerning Storage tank for liquefied gas at low temperature.

The present invention results in very important improvements in the said patent, more particularly over connection with the constitution of the insulating layer and of the sealing barrier. In the said patent, the reservoir was constituted according to techniques which were designed by the applicants for the manufacture of methane-carrier ships provided with integrated tanks.

However, the problems arising in connection with a methane-carrier ship are quite different from those arising in connection with a stationary storagereservoir. Two essential differences should be pointed out in this connection.

In the first place, a methane-carrier ship is subjected to swell and the tanks must be capable of withstanding considerable dynamic stresses caused by the motions of the ship and the resulting motions of the liquefied natural gas contained in the tanks; in addition, the reservoirs are subjected to distortion caused by the deformation of the beam formed by the ship. As a result, each element of the insulating layer and of the sealing barrier must be, on the one hand, suitably attached to the shell and, on the other hand, allowed to deform freely firm soil, or possibly immersed in the sea so as to be anchored on its bottom which may be the continental shelf. The substantially circular cylindrical reservoir may have, for instance, the following dimensions: diameter: 50, 80, 100 andeven 120 meters, height: from 20 to 35 meters. Such reservoirs are designed for storage, over long periods, for instance several months, of very large amounts of liquefied natural gas. The amounts produced in excess during low-consumption periods may thus be liquefied and stored in order to be reutilized subsequent to regasification several months later.

Under such conditions, it is necessary, in the first place, that the gasification ratio be very low for instance, it may be required that the evaporation during the storage period should not exceed 0.04 percent per day. Under such conditions, it has been established by way of calculations and experience that considerable thicknesses of heat-insulating material must be used, at least in order to cover the reservoir side wall. Now the techniques using juxtaposed cases filled with insulating material and attached to the side wall, described particularly in the aforementioned patent, are hardly applicable, for they would lead to prohibitive costs together with considerable weight.

On the other hand, since the reservoir of the invention is intended to be mounted on firm soil, the inner enclosure is not subjected to dynamic stresses, but only the static stress resulting from the pressure of the storage liquefied gas. This stress increases from the base of the reservoir to its top. Under such conditions, it is altogether unnecessary to provide for such a highly rigid and resistant structure as the one resulting from the said juxtaposed cases. Moreover, it is desirable, from the economic point of view, to use an insulating layer whose crushing strength diminishes from the base of the reservoir to its top, the said strength corresponding every time to the maximum static pressure of the liquefied gas. a

In short, the invention provides novel means which are particularly well-adapted and suitable for the specific problems involved in the reservoir for the storage, over long periods, of very large amounts of liquefied natural gas, the said reservoir being mounted either on firm soil and/or adapted to be immersed to rest on the bottom of the sea being, for example the continental shelf. l i

A reservoir according to the invention, of the general type described above, is characterized particularly in that in order to form, in contact with the reservoir sidewall, a layer of heat-insulating material whose thickness and, therefore, efficiency are much greater than those of the layers known up to the present, while at the same time insuring structural simplification, weight'reduction and lower cost together with the desired freedom of deformation of the reservoir, the said heat-insulating layer is formed of vertical juxtaposed caissons which are constituted i a. by radial panels made from wood, plywood, agglomerated glass fibres or'the like, and, if desired, partially filled with rock wool, glass wool, expanded foam or the like, the said panels being arranged edge to edge, vertically above one another, substantially up to the top of thereservoir side-wall and being fastened to the sidewall by means of studs and metal fittings previously placed in vertical lines on the internal face of the reservoir side-wall;

b. by front panels made from wood, plywood, agglomerated glass fibres or the like, and, if desired, partially filled with rock wool, glass wool, expanded foam or the like, the said panels being arranged side by side, but with a clearance between one another, and resting on the radial inner edges of the said radial panels, onto which they are locked by any suitable locking means which are advantageously provided with grooves intended to receive the said joint-plate,

the length of the said panels and the said front panels being substantially the same, for instance ranging about 1.80 meters to 2 meters in order to ensure easy han dling.

Thus, considerably structural simplification and cost reduction is attained as compared with the structure consisting of juxtaposed cases proposed in the aformentioned French patent. However, such a reducedweight structure preserves the individuality of the front panels and gives them freedom of motion with respect to one another. This is very important owing to the fact that the outer resistant enclosure of the reservoir will be deformed under the action of the external'differential temperatures which will cause its diameter to vary. Displacements of several centimeters may thus occur at the level of the insulating layer. Such deformations will be readily absorbed by the proposed free mounting of the various radial and front panels which may move on one another and against one another.

According to another feature of the invention, there are provided struts resting by one of their ends upon the said radial-panel fastening metal-fittings,the said struts being made from wood, glass fibres or the like and mounted angularly, for instance substantially horizontally and at an angle of 45 with respect to the radial direction of the point considered,whereas on the said front panel, on the inner face turned towards the side wall, shoes are provided which receive the otherends of the said struts, adjusting means being provided to adjust the bearing of each shoe upon its associated strut, the said struts forming a bracing for the said front panels to avoid their crushing under the action of the pres sure of the liquefied gas contained in the reservoir.

Thus, the caissons forming the resistant structureof the insulating layer may reach the required rigidity to withstand the static efiort of the stored liquefied gas, even with considerable thicknesses, ranging for instance about 1 meter, of the said layer. At each level, the struts, their number and their distribution may be adapted to offer the required resistance to the static pressure of the liquefied gas. The mounting operation is very simple, for it is sufficient to first position the radial panels, for instance on a vertical line from the base to the top of the reservoir, thereafter to position the struts, and then to place the front panels and secure them on the radial panels and, lastly, simply adjust the bearing of the struts in order that they may correctly fulfill their bracing function. Owing to the considerable mounting tolerances allowed by such an assembly and to the freedom of motion of each panel with respect to the others, all the elements may be prefabricated by conventional woodworking methods without it being necessary to comply with stringent manufacturing tolerances. Heat insulation subsequent to mounting of the caissons is obtained simply by filling them, for instance, with suitably vibrated and compressed perlite.

According to another feature of the invention, an expansion corrugation being provided, as known per se, at the base of the reservoir and interconnecting the Invar sealing membranes covering respectively the reservoir bottom and wall, the said corrugation is secured. on the one hand, to the structure of the vertical supporting insulation which is applied against the reservoir wall, and it is secured on the other side on insulating caissons adapted to slide radially while at the same time being retained on the reservoir bottom by cables or the like, the said corrugation resting, with its concavity turned upwards, upon a supporting insulating layer which is advantageously resiliently deformable. In this manner, the expansion corrugation is not liable to be crushed under the action of the static pressure of the liquefied gas, and it may be made from thin sheetmetal, for instance lnvar. Its fastening,on its inner edge, on caissons adapted to slide radially enables the differential expansions between the reservoir bottom wall and side-wall to be absorbed, especially the displacements of the side wall under the action of the differential heat variations caused particularly by sunning.

The invention will appear more clearly from the following detailed description, made with reference to the appended drawings, illustrating by way of example one form of structure and a few modified forms according to the invention. In the said drawings FIG. l'is a horizontal sectional view showing diagrammatically one quarter of the reservoir surface FIG. 2 is a vertical sectional view showing diagrammatically'one half of the reservoir FIG. 3, is a view,to a larger scale, of the encircled portion III of FIG. 1, showing how the supporting insulating layer is constituted in contact with the reservoir side-wall FIG. 4 is an exploded view showing how the radial panels, the front panels and the struts serving to form the caissons of the supporting insulating layer are mounted so as to co-operate FIG. 5 is a sectional view substantially upon the line V--V of FIG. 3

FIG. 6 isa diagrammatical and developed view, to a smaller scale, of the mounting of the radial panels on the reservoir side-wall FIG. 7 is a sectional view substantially upon the line VII-VII of FIG. 6;

FIG. 8 is a view similar to that of FIG. 6, showing a subsequent stage wherein the front panels have just been positioned FIGS. 9 and 10 are two perspective views illustrating the positioning of the strut ends respectively on the rear of a front panel and ona metal fitting of a radial panel;

FIG. 11 is a diagrammatic plan viewof a front panel;

FIG. 12 is a side view of the panel illustrated in FIG. 11

FIG. 13 is a top view of a radial panel FIG. 14 diagrammatically illustrates the mounting of four front panels resting upon two radial panels whose thickness is considerably exaggerated for the sake of clarity of the drawing FIG. 15 is an enlarged view showing in detail the encircled portion XV of FIG. 3 ilIustrating the mounting of the sealing membrane and its fastening on the front panels FIG. 16 is a vertical sectional view illustrating the sealing of the roof;

FIG. 17 is a vertical sectional view showing how the vertical sealing barrier and the horizontal sealing barrier are interconnected at the reservoir base by an expansion corrugation FIG. 18 is a diagrammatic top view, with parts broken away, of other details of the connection illustrated in section in FIG. 17 in this FIG. 18 the curvature of the reservoir side-wall is considerably exaggerated for the sake of clarity FIG. 19 is a sectional view, to a larger scale, of the connecting zone encircled at XIX in FIG. 17

FIG. 20 is a view similar to that of FIG. 3, to a smaller scale, illustrating a modified form of embodiment wherein a double sealing barrier is used FIG. 21 is an enlarged and detailed view of the encircled portion XXI of FIG. 20, relating to the mounting and the fastening of the double sealing barrier on the front panels of the insulating layer FIG. 22 is a view, to a smaller scale, similar to that of FIG. 17 and relating to a modified form of embodi ment wherein the expansion corrugation provided at the reservoir base to interconnect the vertical sealing member and the horizontal sealing member is divided into two half-corrugation and FIG. 23 is a view similar to FIG. 16, but to a smaller scale, showing the sealing of the roof in case a double sealing barrier is used.

Reference is first made to FIGS. 1 and 2 showing a reservoir 30 for the storage of liquefied natural gas at very low temperature and substantially at atmospheric pressure according to the invention. The reservoir is essentially constituted by a rigid outer enclosure comprising a reinforced .concrete bottom-wall 31 resting upon a foundation 32, a prestressed reinforced concrete side-wall 33 and a reinforced concrete vault 34 from which is suspended, by means of cables 35, a roof 36 comprising beams 37 upon which rests a heatinsulating layer 38.

On the bottom-wall 31 are arranged juxtaposed n'gid cases 39 filled with perlite forming an insulating layer 40 for the reservoir bottom. The said cases may be, for instance, of the same nature and have the same structure as those used to form the lower insulating layer of the reservoir described in the aforementioned patent.

The lateral insulating layer 41 covering internally the side wall 33 of the reservoir is constituted by juxtaposed caissons 42, as will appear later and particularly during the description of FIG. 3. The thickness of the layer 41 may be considerable, ranging for instance up to about 1 meter.

The inner sealing barrier of the reservoir is constituted, in the same manner as described in the aforesaid patent, by a thin Invar sheet coating, the thickness of which is for instance three tenths of a millimeter. On the bottom of the reservoir, the sealing membrane is constituted by parallel strips 43 which are unrolled (FIG. 1) on the insulating layer 40 and whose borders raised at an angle of 90 towards the interior of the reservoir are welded edge to edge on metal strips secured on the heat-insulating layer 40 as mentioned in the aforesaid patent. On the lateral wall of the reservoir, the sealing membrane is constituted, in the same manner as that of the bottom, by juxtaposed Invar strips 44 whose borders raised at an angle of 90 towards the interior of the reservoir, are welded edge to edge on metal strips secured on the heat-insulating layer 41 as will appear more clearly hereinafter and more particularly during the description of FIGS. 3 and 15.

The sealing membranes, respectively 45 covering the reservoir bottom and 46 covering the lateral wall of the reservoir, are sealingly interconnected by an expansion corrugation 47 provided at the base of the reservoir and whose structure will be described in detail later, more particularly during the description of FIGS. 17 to 19.

Roof fluid-tightness is ensured by a supple film made by a complex of plastics and metals or the like 48, the mounting of which will appear more clearly during the description of FIG. 16. The said supple film covers the surface of the roof'36 suspended under the concrete vault 34.

The constitution of the lateral insulating layer 41 will now be described with particular reference to FIGS. 3 to 15.

As appears particularly from FIG. 3, the heatinsulating layer 4 is formed of vertical juxtaposed caissons 42. Each caisson 42 comprises a. radial panels 50 which, in the example illustrated, are constituted by two plywood sheets 51, 52, assembled on wooden lath braces 53 and 55 whose internal empty spaces 56, 57 are stuffed with an insulating material such as for instance rock wood b. front panels 60 which, in the example illustrated, are constituted by two plywood sheets 61, 62,braced by wooden laths, for instance two end laths 63, 65, and four intermediate laths 64. The internal spaces 66 are advantageously filled, as in the radial panels, with a heat-insulating material such as rock wool or the like c. struts 70 forming a bracing for the front panels 60. The mounting and forming of the caissons 42 may be carried out as follows Studs are anchored in vertical lines in the concrete of the side wall 33 of the reservoir. In case the side wall is constituted by metal, the studs are arranged in the same manner and are for instance secured by welding. The marking of the vertical lines may be accurately performed by means of a laser. The studs are so arranged as to allow the fixing of metal fittings 81 (FIGS. 3, 5 and 10) which will enable the radial panels 50 to be attached to the reservoir side-wall. When all the studs 80 are thus mounted and suitably distributed, as will be explained later, the yertical radial panels can be arranged above one another in vertical lines by mounting successively the panels 50a, 50b, 50c, '50d, 50c, and so on (FIG. 6), up to the top of the reservoir. These panels have advantageously a height ranging about 1.80 meters to 2 meters, so that they can be readily handled. The handling is performed from a vertical tower or turret mounted in the reservoir. When the edge-to-edge mounting on such a vertical tier of radial panels is completed, the following tier may be mounted by attaching the panels 50p, 50q, 50r and so on, and then the following tiers successively. Each radial panel is fixed on its metal fittings 81 by means of wood screws 82 which are received in orifices 83 of the fittings 81. The screws 82 are tightened in the wood core 53 of the panel 50. Usually, the metal fitting 81 is initially mounted on the corresponding edge 58 of the panel 50 and then the nuts 84 are tightened to fasten the fittings on the studs 80.

When two or three tiers of contiguous vertical radial panels are thus assembled as illustrated in FIG. 6, the

struts 70 are positioned horizontally between the plates 85 of the fittings 81 (FIG. 10).

On this structure are then positioned the front panels 60, beginning from the base, i.e., mounting successively the panels 60a, 60b, 60c, 60d and so on (FIG. 8).

As seen more clearly in FIG. 3, between two front panels 60 is provided a large clearance 68 the function of which will appear later. In order to enable the front panels 60 to be mounted and secured, grooves 69, (FIGS. 3 and 11) are provided on the lateral edges of the panels 60, so that one and the same locking tongue 86 forming a joint-plate enables two adjacent parallel edges of two adjacent frontal panels 60 to be maintained applied against the adjacent radial panel 50. The locking tongue 86 is fastened on the edge 59 of the radial panel by means of bolts 87 which are mounted (FIGS. 3, 4 and 13) in the cross-beam forming the edge 59 of the panel 50. The locking of the tongue 86 is performed on the bolts 87 by means of sunk nuts 88 (FIG. 3). As appears from FIG. 13, three bolts such as 87 may be provided for instance on the edge 59 of the panels 50.

As appears more clearly from FIGS. 3, 4, 9 and 10, the bracing struts rest, at one of their ends, in the metal fittings 81 between the plates on the side wall 33 of the reservoir, and, at their other end, on metal shoes 90 which are secured by means of wood screws 91 in beams 92 on which are applied the front panels 60. The beams 92 themselves are mounted on metal fittings 93 (FIGS. 3 and 4) which are mounted by means of threaded rods 94 and nuts 95 on the edge 59 of the panels 50. Wood screws 96 enable the beams 92 to be mounted on the lateral bearing flanges 97 of the fittings 93. In FIG. 8 there are shown seven beams 92 which are thus mounted on the bracing struts 70 and ready to receive front panels 60.

Each shoe 90 comprises an adjusting screw 98 which, by being screwed through a tapped hole 99, and pressing on a metal plate 100, enables each strut 70 to be suitably positioned to correctly fulfill its bracing function, thus taking up all the manufacturing tolerances The caissons 42 are mounted in the following sequence a. marking and placing the studs 80 b. mounting, in vertical lines, of juxtaposed radial panels whose edge is provided with metal fittings 81, and assembling of the same panels by mounting the nuts 84 c. positioning of the struts 70 d. positioning of the beams 92 on the struts, assembling and adjustment of the bracing e. mounting of the front panels 60 and tightening by screwing the nuts 88 on the bolts 87 passing through the locking tongues 86 forming joint-plates.

In such a structure, considerable deformations are possible at the line ofjunction of the various front panels, so that the deformations of the side wall will result, at the level of the insulating layer, in corresponding deformations which will by no means be detrimental to the mechanical resistance of the insulating layer 31 by which the pushing forces of the liquefied gas contained in the reservoir are finally supported.

Owing to the fact that the static pressure caused by the liquefied gas is proportional to its height in the reservoir, the number, distribution and resistance of the struts are so selected as to enable them to withstand at each point the maximum force to be supported. Thus,

for instance, in FIGS. 6 and 8, there is shown a distribution of the struts, according to which, in the lower portion of the reservoir, three sets of two struts are provided for each front panel, whereas in the medial portion only two sets are provided and in the upper portion only one set.

In order to facilitate the mounting and assembling of the front panels as well as the radial panels, between the various superposed radial and front panels are advantageously provided laths or the like forming tenons ensuring the junction and vertical alignment of the panels, in the vertical edges of which are provided corresponding mortises. In FIGS. 11 and 12 is shown a lath forming a locking tenon 101 inserted in the mortises 102 of two superposed front panels. Likewise, in FIG. 13, a lath forming locking tenon will be inserted into the vertical edges 104 of a lower radial panel and 105 of an upper radial panel.

The mounting and fastening of the sealing barrier on the insulating layer 41 will now be described.

To this end, as seen more particularly in FIGS. 3 and 15, the external surface of the front panels are provided with slots 106. More specifically, as appears from FIG. 15, the slot 106 is formed in the upper plywood layer 61 of the panel 60, and, as appears from FIG. 11, it extends over the whole length of the panel. It is composed of a substantially rectangular cut milled in the bearing surface 61 of the panel, and another slot 108 extends on one side of it under the bearing surface of the panel. In the slot 108 is engaged the horizontal bar of a T- shaped member 109 made from Invar or any other metal which is resilient at low temperature and whose coefficient of thermal expansion is low. A rod 110 forming a locking shoulder for the profile member 109 maintains the latter in the cut 108. The leg 109a of the member 109 thus projects into the interior of the reservoir on the bearing surface of the panel 60. On this projecting portion are secured, by continuous seamwelding, the two raised borders of two adjacent Invar strips 44 forming a lateral sealing membrane of the res ervoir.

According to the embodiment illustrated in FIG. 3, two slots 106 are provided for each front panel and one similar, parallel slot 107 for each joint-plate 86. The sealing membrane 46 is thus reliably attached to its supporting insulating layer, but it can freely expand in the vertical direction. Moreover, owing to the raised borders of the said juxtaposed invar strips, a good resiliency is imparted to the whole assembly, which can thus follow all the deformations resulting from the motion of the front panels under the action of the differential expansions of the concrete side-wall 33.

As seen in FIGS. 3' and 14, orifices 112 are provided in the outer plywood layer6l of the front panels 60. The said orifices are provided in order that, in case of breakage of the sealing membrane 46, the liquefied gas i coming into contact with the hot panel 60 and evaporating in the internal volumes 66 of the said panel may escape through the orifices 112 without deforming the panels. Further, the panels being mounted in superposition and passageways 200 being provided in the locking laths 101 (FIG. 11), all the front panels of one and the same vertical row communicate with one another and form a channel enabling the gas formed as a result of local breakage of the sealing membrane to escape through the upper portion of the reservoir.

Reference is now made to FIG. 16 illustrating the mounting of the reservoir roof.

On the last vertical caissons 42 are placed, after introduction, compression and suitable vibration of the perlite within each vertical caissons 42 related to .the whole height of the reservoir, plywood plates 120 forming a cover for the insulating layer. Fluid-tightness between the side wall 33 and the plates 120 is ensured by a membrane made from a complex of plastics and metal or the like 121, extending all around the reservoir.

Likewise, the sealing sheet 48 covering the reservoir roof 36 is sealingly fastened at 122 on the plates 120. On the plates 120 and the beams 37 of the roof 36 are placed bags filled with glass wool, perlite or the like 123 ensuring reliable heat-insulation of the roof.

The sealed connection between the vertical lateral sealing membrane and the horizontal sealing membrane at the reservoir base will now be described by referring more particularly to FIGS. 17 to 19.

In a manner known per se, the reservoir is so designed that the side wall 33 may move radially on the bottom wall 31 owing to a sliding joint formed for instance by steel sheets 131, 132 sliding on one another and interconnected by a deformation corrugation 133. In any case, relatively important radial displacements of the side wall 33 must be allowed to take place on the bottom wall 31. The said motions are of great significance since the dimensions of the reservoir are quite considerable and it is very sensible to the sunning conditions varying in time.

During such a radial displacement of the bottom wall on the side wall, which displacement may be important on the south and small on the north at a given hour of the day, the insulating layer 41 mustfollow the side wall since it is attached thereto and is deformed in a corresponding manner. The same applies to the sealing membrane 46. This will result in important displacements between the foot of the vertical membrane 46 and the periphery of the sealing membrane 45, which is not subjected to such deformations.'The membranes 46 and 45 are interconnected by means of a deformation joint constituted by an expansion corrugation 47.

Usually, the expansion corrugations used have their convexity turned upwards, so as to reduce thermal losses. In the case considered, such a constructionis not used,for-, owing to the considerable dimensions of the reservoir, the expansion corrugation may be crushed by the static pressure of the liquefied gas unless it is made extremely thick. According to the invention, the corrugation 47 therefore has its concavity turned upwards, so as to rest continuously upon an insulating layer 134 shaped accordingly. This insulating layer may comprise for instance relatively rigid blocks 135, 136 made for instance from expanded polyvinyl chloride such as the one known under the registered trademark Klgcell, and relatively more supple and elastic blocks 137, 138 made from rock wool, supple expanded polyurethane or the like.

The corrugation 47 is secured, on one side (FIG. 17), by a welded extension 47a by means ofa screw 1391' on blocks 191 solid with the supporting structure of the reservoir, and, on the other side and as appears more clearly from FIG. 19, the corrugation 47 is secured by means of a screw 139 on insulating caissons 140 which may slide radially on other insulating caissons 141. To this end, the caissons 140 are attached to the bottom wall by means of cryogenic steel cables 142 mounted on the sides of the caissons 140, thus preventing the caissons from rising but leaving them free to move radially. The lower surface of the caissons 140 comprises a sliding surface in contact with the upper face 143 of the caissons 141. The caissons 140 and 141 are filled with any suitable heat-insulating material such as for instance perlite or rock wool.

The sealed connection with the horizontal membrane 45 is obtained by welding its peripheral edge to the horizontal portion 147 of the expansion corrugation 47, beyond the screws 139. The weld is shown in FIG. 19 at 144.

Sealed connection with the vertical membrane 46 is obtained by welding its lower edge on the vertical portion of the expansion corrugation 47.

The connection with the panels 39 constituting the insulating layer resting upon the bottom wall 31 of the reservoir is made by means of wooden or plywood panels 145 cut according to needs and to the required dimensions and which rest, on one side, upon the edge of the cases 39 and, on the other side, upon the edge of the upper surface of the caissons 140, the said edge being provided with a-cut 146 for this purpose. The cut 146 also allows for radial displacements of the caissons 140. In order to facilitate the operations, the Invar strips 43 may be stopped before reaching the portion 147 of the expansion corrugation 47, and connecting strips 148 may be cut and dimensioned according to needs.

In FIGS. 17 and 19 are shown at 150 the hooks for attaching the caissons 140 on the reservoir bottom wall by means of cables 142.

' The space comprised between the caissons 140, 141 and the cases 39 is filled with more or less deformable and compressible insulating blocks 151 made for instance from expanded polyvinyl chloride. The blocks 151 and the caissons 150 may be interconnected by means of a stuffing of expanded foam, rock wool or the like. Advantageously, the cases 39 are attached by means of cables 252 to the bottom wall, so as to be prevented from rising and to offer a suitably plane surface during construction.

In order to facilitate the making of the expansion corrugation 47, the latter is advantageously constituted by juxtaposed, substantially rectilinear sectors which, seen from above, are in the shape of isosceles trapezia approximating rectangles. The weld lines of these various sectors are shown at 154 in FIG. 18.

Referring now to FIGS. 20 and '21, there is seen modified embodiment wherein a double sealing membrane is used. In these Figures, the same reference figures have been used to indicate the same members as in the previous Figures. Thus, in FIG. 20, there are shown the caissons 42 forming the supporting insulating layer resting against the concrete side-wall 33 of the reservoir. The caissons are constituted essentially by radial panels 50 on which rest the front panels 60 braced by the struts 70. The constitution of the insulating layer 41 is therefore similar to the one described .in connection with FIG. 3.

In the modification illustrated in FIGS. 20 and 21*, there are provided two sealing membranes, respectively and 161, applied on the insulating layer 41, with an interposed, mechanically resistant heatinsulating layer 162 constituted, for instance, by a material known under the registered trademark foam glass, expanded polyvinyl chloride or polyurethane foam.

This modification may be advantageous in that the presence of a secondary barrier enables either the importance of the cryogenic characteristics (especially the pre-stress ratio) of the concrete constituting the outer resistant shell to be reduced, or the said shell to be made from non-cryogenic materials such as ordinary steel, while at the same time preserving high safety of the structure as a whole.

The fixing is performed, as illustrated in FIG. 21, in a manner quite similar to that described in connection with FIG. 15. Instead of metal strips 109 locked in the slots 108 formed in the plywood layer 61 of the panels 60, longer strips 163 are mounted in a similar manner. In the example illustrated in FIG. 21, a strip 163 is L- shaped in section and is locked by a rectangular rod 164. However, a T-section strip as shown in FIG. 15 may be used as well, provided the leg 16311 of the strip 163 is sufficiently long to enable the two barriers 160, 161 to be secured together with an interposed insulation layer 162.

The membranes 160 and 161 are of course constituted, in the same manner as the membrane 106, by juxtaposing Invar strips '44 whose borders raised at an angle of 90 towards the interior of the reservoir are welded on the portion 163a of the metal strip 163, as shown at 165. The membrane 161 is constituted in a similar manner by juxtaposing Invar strips 44 whose borders raised at an angle of 90 welded, as shown at 166, on the portion 163a of the strip 163.

Reference is now made to FIG. 22 illustrating'a modified embodiment of the expansion corrugation interconnecting the vertical sealing membrane covering the reservoir side-wall and the horizontal sealing membrane covering the bottom. In FIG. 22 the same reference digits are used to indicate the similar elements shown in FIG. 17.

The essential difference between the embodiment of FIG. 22 and that of FIG. 17 is that the expansion corrugation 170 interconnecting the vertical sealing membrane 46 and the horizontal sealing membrane 45 is divided into two half-corrugations 171, 172 whose concavity is turned upwards. Another difference results from the fact that in FIG. 22 the expansion corrugation is double, for it interconnects the two superposed vertical membranes 160, 161 and the two superposed horizontal membranes 173, 174 of the reservoir, this example corresponding to the case where use is made of two superposed sealing membranes separated by an insulating layer, respectively, 162 and 175.

The radial displacements of the sealing barrier 46 with respect to the sealing barrier 45 are absorbed, in the same manner as in FIG. 17, by the deformation of the two resilient deformable half-corrugations 171, 172. The half-corrugation 171 is constituted by two lnvar half-corrugations 176, 177 separated by an insulating layer 178 and which are welded on one side to the membranes 160, 161 respectively and secured by means of screws to the structure of the vertical supporting insulation. At its other end, the half-corrugation 176 is secured to an insulating block 179 made for instance from wood and for instance in the same manner as the half-corrugation 47 is secured to the panel 140 (FIG. 19). The block 179 is attached by means of cryogenic steel cables 180 to the bottom wall of the reservoir and is adapted to slide and move radially on the surface 133 of the panel 141. The half-corrugation 177 is secured in the same manner to a wooden block 181 resting upon the block 179.

I Likewise, the half-corrugation 172 is constituted by two Invar gutter-shaped elements 182, 183 separated by an insulating material 184. The gutter-shaped element 182 is secured on one side to the block 179 and on the other side to a block 185 attached by a cryogenic steel cable 186 to the bottom wall of the reservoir,so that the block 185 may slide radially on the surface 140 of the casing 141. The upper corrugation 183 is secured on one side to the block 181 and on the other side to a block 187 resting upon the block 185. The deformation and displacements take place in the same manner as described in connection with FIG. 17. At 188 there is seen a filling insulating material such as for instance rock wool, filling the empty space between the cases 39 and the adjacent caissons 141 as well as the blocks 185.

Sealings at various locations are ensured by welding and overlapping of Invar sheet-metal, especially on the screw heads, enabling the expansion half-corrugations to be secured to the various blocks. Thus, 189 and 190 indicate Invar plates welded on the adjacent portions of two half-corrugations, respectively 176, 182 and 177, 183.

As in FIG. 17, the base of the front panels 60 rests upon wooden blocks 191 which themselves secured rigidly on caissons 192 firmly attached by means of bolts 193 to the bottom wall 31. A sliding surface 194 is provided at the same of the panels 60 on the blocks 191 so as to allow for free expansion of the insulating layer 41 during the radial displacement of the side wall on the bottom wall.

Referring now to FIG. 23, there is shown how the sealed connection of the roof is ensured in case a double sealing membrane 160, 161, is used, to form the lateral sealing layer 46 of the reservoir. It will thus be noted that the two sealing membranes 160, 161 are interconnected at their lower portion by welded joints.

Owing to this arrangement, when the reservoir is entirely assembled, an overall sealing test of the two reservoir membranes may be carried out by introducing between the membranes a tracing gas at a predetermined pressure and by measuring any possible losses of this gas during a given period of for instance 24 or 48 hours. If the test reveals no leakage, then it may be considered that both membranes are completely fluidtight.

Of course, the invention is by no means limited to the fonns of construction and embodiments described hereabove by way of example, the invention comprising all technical equivalents to the means described as well as their combinations, should the latter be carried out according to its spirit and within the scope of the following claims. In particular, the struts 70 may be advantageously moulded from agglomerated glass fibres, thus reducing the weight of the structure. Also, the front and/or radial panels may be provided with crossbeams moulded from agglomerated glass fibres.

What is claimed is:

1. Reservoir for the storage of liquefied gas at very low temperature having a base and being adapted to be mounted permanently on a firm ground, of the type comprising an outer rigid shell comprising a heatinsulated bottom wall, a side wall and a cupula shaped cover, a thick heat-insulating layer comprising vertical caissons filled with insulating material, said caissons being mounted side by side and covering internally the greater part of the side wall, and at least one sealing barrier secured to and against said heat-insulating layer and comprising a thin sheet of a metal which is resilient at low temperature and has a low coefficient of thermal expansion, said heat-insulating layer resisting deformation forces occurring in use of the reservoir, said vertical caissons being juxtaposed and each comprising:

a. radial panels of thin, heat-insulating strong material, said panels being arranged edge to edge, vertically one above the other, substantially to the top of said reservoir side-wall and means for securing said panels to said side-wall comprising studs and metal fittings pre-arranged in vertical lines on the inner face of the reservoir side-wall;

b. front panels of thin, heat-insulating strong material, said front panels being arranged side by side with a clearance between one another, and resting upon the inner radial edges of said radial panels, locking bolts secured to said radial panels and whose threaded shanks project towards the interior of the reservoir on said radial panels,. locking means mounted on said bolts to lock said front pan- I els to said radial panels, loclting tongues forming joint-covers which rest astride upon two adjacent edges of two adjacent front panels each provided with grooves intended to receive said joint-covers, said locking means resting upon said locking tongues,

the lengths of said radial panels and of said front panels being substantially the same for easy handling and said heat-insulation filling said caissons being light, yieldable heat-insulating material.

2. Reservoir according to claim 1, comprising cable elements, an expansion corrugation means at the bottom wall of said reservoir and which interconnects respective sealing barriers which cover bothsaid bottom and side wall of the reservoir, wherein said corrugation means is secured on said insulating caissons, said caissons being slidingly movable on said bottom wall for radial displacement and loosely attached to the reservoir bottom by said elements, and a bearing insulating layer which is resiliently deformable upon which said corrugation means rests.

3. Reservoir according to claim 1, wherein said radial panels and said front panels respectively are each comprised of two parallel inner and outer sheets of rigid heat-insulating material separated .by spacing pieces, separating said sheets and a-said light, yieldable heatinsulating material being located between said spaced sheets.

4. Reservoir according to claim 3, wherein the outer sheet of each of the front panels is provided with openings communicating with the internal space comprised between the said two sheets of each of said front panels.

5. Reservoir according to claim 1, wherein beams are mounted horizontally against the inner face of said front panels between two adjacent radial panels and wherein struts of rigid heat-insulating material rest, at one of their ends, upon said metal fittings to which said radial panels are attached, said struts being mounted substan-tially horizontally and extending angularly at an angle of about 45 with respect to the radial direction at the mounting location and shoes provided on the innerface of said beams directed towards said side wall and which receive the other ends of said struts, and adjusting means to adjust the extent of bearing of each shoe on its associated strut, said struts forming a bracing for said front panels to prevent their being crushed under the pressure of the liquefied gas contained in the reservoir.

6. Reservoir according to claim 5, wherein the number of said struts mounted .on said side-wall decreases from the base to the top of said side-wall.

7. Reservoir according to claim 5 wherein said struts mounted on said side wall are disposed so as to provide progressive decreasing bracing from the base to the top of said side wall.

8. Reservoir according to claim 1, wherein tenons ensure the connection and vertical alignment of the panels, the vertical edges of said panels being provided with corresponding mortises.

9. Reservoir according to claim 8, wherein said tenons which ensure the connection and the vertical alignment of the front panels are provided respectively with vertical apertures.

10. Reservoir according to claim 1, wherein said front panels, as well as said locking tongues forming joint covers therefor, each have on the respective outer surfaces thereof vertical slots constituted by a substantially rectangular cu't provided on said outer surface and prolonged under this surface onone side of said cut, a horizontal bar member being received in each slot, a rod forming a locking shoulder for each member also located in each slot, and each said sealing barrier comprising a thin sheet of metal having a low coefficient of thermal expansion, maintained against the outer surface of a said front panel.

welded onto said members.

a: r a: 

1. Reservoir for the storage of liquefied gas at very low temperature having a base and being adapted to be mounted permanently on a firm ground, of the type comprising an outer rigid shell comprising a heat-insulated bottom wall, a side wall and a cupula shaped cover, a thick heat-insulating layer comprising vertical caissons filled with insulating material, said caissons being mounted side by side and covering internally the greater part of the side wall, and at least one sealing barrier secured to and against said heat-insulating layer and comprising a thin sheet of a metal which is resilient at low temperature and has a low coefficient of thermal expansion, said heat-insulating layer resisting deformation forces occurring in use of the reservoir, said vertical caissons being juxtaposed and each comprising: a. radial panels of thin, heat-insulating strong material, said panels being arranged edge to edge, vertically one above the other, substantially to the top of said reservoir side-wall and means for securing said panels to said side-wall comprising studs and metal fittings pre-arranged in vertical lines on the inner face of the reservoir side-wall; b. front panels of thin, heat-insulating strong material, said front panels being arranged side by side with a clearance between one another, and resting upon the inner radial edges of said radial panels, locking bolts secured to said radial panels and whose threaded shanks project towards the interior of the reservoir on said radial panels, locking means mounted on said bolts to lock said front panels to said radial panels, locking tongues forming joint-covers which rest astride upon two adjacent edges of two adjacent front panels each provided with grooves intended to receive said joint-covers, said locking means resting upon said locking tongues, the lengths of said radial panels and of said front panels being substantially the same for easy handling and said heatinsulation filling said caissons being light, yieldable heatinsulating material.
 2. Reservoir according to claim 1, comprising cable elements, an expansion corrugation means at the bottom wall of said reservoir and which interconnects respective sealing barriers which cover both said bottom and side wall of the reservoir, wherein said corrugation means is secured on said insulating caissons, said caissons being slidingly movable on said bottom wall for radial displacement and loosely attached to the reservoir bottom by said elements, and a bearing insulating layer which is resiliently deformable upon which said corrugation means rests.
 3. Reservoir according to claim 1, wherein said radial panels and said front panels respectively are each comprised of two parallel inner and outer sheets of rigid heat-insulating material separated by spacing pieces, separating said sheets and a said light, yieldable heat-insulating material being located between said spaced sheets.
 4. Reservoir according to claim 3, wherein the outer sheet of each of the front panels is provided with openings communicating with the internal space comprised between the said two sheets of each of said front panels.
 5. Reservoir according to claim 1, wherein beams are mounted horizontally against the inner face of said front panels between two adjacent radial panels and wherein struts of rigid heat-insulating material rest, at one of their ends, upon said metal fittings to which said radial panels are attached, said struts being mounted substan-tially horizontally and extending angularly at an angle of about 45* with respect to the radial direction at the mounting location and shoes provided on the inner face of said beams directed towards said side wall and which receive the other ends of said struts, and adjusting means to adjust the extent of bearing of each shoe on its associated strut, said struts forming a bracing for said front panels to prevent their being crushed under the pressure of the liquefied gas contained in the reservoir.
 6. Reservoir according to claim 5, wherein the number of said struts mounted on said side-wall decreases from the base to the top of said side-wall.
 7. Reservoir according to claim 5 wherein said struts mounted on said side wall are disposed so as to provide progressive decreasing bracing from the base to the top of said side wall.
 8. Reservoir according to claim 1, wherein tenons ensure the connection and vertical alignment of the panels, the vertical edges of said panels being provided with corresponding mortises.
 9. Reservoir according to claim 8, wherein said tenons which ensure the connection and the vertical alignment of the front panels are provided respectively with vertical apertures.
 10. Reservoir according to claim 1, wherein said front panels, as well as said locking tongues forming joint covers therefor, each have on the respective outer surfaces thereof vertical slots constituted by a substantially rectangular cut provided on said outer surface and prolonged under this surface on one side of said cut, a horizontal bar member being received in each slot, a rod forming a locking shoulder for each member also located in each slot, and each said sealing barrier comprising a thin sheet of metal having a low coefficient of thermal expansion, maintained against the outer surface of a said front panel.
 11. Reservoir according to claim 10, wherein each sealing barrier comprises two thin sheets of a metal that is resilient at low temperature and has a low coefficient of thermal expansion, and an insulating layer between said sheets for separation thereof, said barrier being welded onto said members. 